Re: nthoutarg function?

[Jordi Gutiérrez Hermoso]

2011/10/14 Jordi Gutiérrez Hermoso <address@hidden>:
> 2011/10/14 John W. Eaton <address@hidden>:
>> On 14-Oct-2011, Jordi Gutiérrez Hermoso wrote:
>>
>> | This blog post got me thinking:
>> |
>> |     
>> http://abandonmatlab.wordpress.com/2010/05/28/multiple-output-arguments/
>> |
>> | The blogger is quite right that multiple output arguments are a
>> | problem. They require temporaries, and this makes for some slightly
>> | brittle code.
>> |
>> | It's not difficult to implement a generalisation of the
>> | "2nd_output_of" function:
>> |
>> |     function out = nthoutarg(fun, n, varargin)
>> |       outargs = cell (1,n);
>> |       [outargs{1:end-1}, out] = fun (varargin{:});
>> |     endfunction
>> |
>> | Should this function be part of Octave? I'm all for prettifying the
>> | language as much as possible.
>>
>> Because the value of nargout can change the behavior of a function,
>> you might need to specify the number of the argument you want and
>> the value of nargout to pass to the function separately. For
>> example, when calling functions like svd. With your definition of
>> nthoutarg,
>>
>>  nthoutarg (@svd, 2, rand (3, 4))
>>
>> fails.  You need something like
>>
>>  function out = nthoutarg (fun, n, nout, varargin)
>>    if (nargin > 2 && nout >= n)
>>      outargs = cell (1, nout);
>>      [outargs{:}] = fun (varargin{:});
>>      out = outargs{n};
>>    else
>>      print_usage ();
>>    endif
>>  endfunction
>
> Right, something like it, except it would be nice to make nout == n by
> default.

I pushed this:

    http://hg.savannah.gnu.org/hgweb/octave/rev/62d1f56b0be7

- Jordi G. H.